Study on the Development Andassessment of a Novelvertical Flow Constructed Wetland System Usingceramsiteas Substrate
|School||Xi'an University of Architecture and Technology|
|Keywords||ceramsitesubstrate vertical flow constructed wetland nitrogen andphosphorous removal wastewater treatment|
Problems, such as land consuming and low removal efficiency on N and Pelements, still exist in the application of constructed wetland. In this paper,a new type ofvertical flow constructed wetland was developed.The constructed wetlandwas made upof an influent distribution system, five parallelwetland units, and an effluent collectionand discharging system.Wastewater flowed down in the distribution system and turnedto upflow in the wetland units. The pollutants removal ratio could be improved notablyby keeping the wetland units running in an intermittent manner, which would help toprevent the occurrence of substrate clogging and keep the the system running stablely.Meanwhile, as it’s simple in installation, low cost in construction and operation, andhigh wastewater treatment efficiency and landscape contribution, the novel constructedwetland equipment would be widely used, especially in rural areas of China withdecentralized wastewater discharge.To improve pollutants removal ability in the wetland system,a new type ofceramsite wetland substrate was also developed in this study by optimizing thecomposition of the raw materials, water ratio, paramenters in the processes ofpretreatment and calcination.Study on the physicochemical characteristics includingspecific area, pollutant dissolving, adsorption capacity, and strength of this newsubstrate showed that its BET surface area was71.47㎡/g; the surface structureappearedto be uniform tiny blockette with a mount of microporous, and the porousdiameters variedbetween1.9-61.0nm,which was good for the bacteria to attach to itssurface. Dissolution test showed that the dissolubility of the new substrate matched thetoxicity standards of GB2002,without the risk of second contamination. Static adsorption experimental result showed that the novel ceramsite substrate couldadsorborganic compounds,ammonium,nitrate,and phosphatenotably in the wastewater.Long-time operation results showed that the novel constructed wetland operatedwith ceramsite substrate had good pollutants removal capacity.When the system reachedstability, the concentration of COD in the effluent was lower than50mg/L,more than80%removed; the concentration of TP in the effluent was lower than0.3mg/L and itsremoval efficiency was higher than95%; the removal ratiosof nitrogen and TN werebotharound80%. Meanwhile, the system also had good resistant capacity to the shocksof hydraulic loading rate,pH, and contaminant loading rate. Its pollutant removalcapacity was much higher than that of quartz sand.Further study on the distributions ofboth dissolved oxgen and pollutants along the water flow in the wetland system showedthat dissolved oxygen content in the wetland substrate contributed to the removal ofmost of the pollutants.Based on the new ceramsite matrix of the vertical flow artificial wetland, covers asmall area, simple installation, low cost of engineering construction and operation,wastewater treatment effect and ecological landscape effect is good. Then the systemhas the broad application prospect, especially suitable for the decentralized sewagetreatment in rural areas.